Reducing discomfort caused by electrical stimulation

ABSTRACT

The invention is directed to a novel method for reducing discomfort caused by transcutaneous stimulation. The novel method includes providing transcutaneous stimulation, reducing the transcutaneous stimulation at a first location, and substantially maintaining the transcutaneous stimulation at a second location. The transcutaneous stimulation may be created by electric and/or magnetic fields. The first location may be relatively proximate to the cutaneous surface and may comprise tissue, nerves and muscle. Also, the second location may be relatively deeper than the first location and include, for example, brain tissue that requires the transcutaneous stimulation for treatment purposes. The invention further may include locating a conductor on a treatment area and/or a transcutaneous stimulation device relative to the first location. In addition, the method may further include adjusting how much the transcutaneous stimulation is reduced at the first location.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority under 35 U.S.C. § 119 (e) from U.S.provisional application Ser. No. 60/452,477, filed on Mar. 7, 2003,entitled “Device, Method, and System for the Reduction of DiscomfortAssociated with and Facilitating Treatment via Magnetic Stimulation,”which is herein incorporated by reference in its entirety. Thisapplication is a continuation of U.S. patent application Ser. No.10/657,296 filed Sep. 8, 2003 entitled “Reducing Discomfort Caused byElectrical Stimulation,” which is herein incorporated by reference inits entirety.

FIELD OF THE INVENTION

The invention relates to the field of electrical stimulation.Specifically, the invention relates to reducing discomfort created byelectrical stimulation.

BACKGROUND OF THE INVENTION

A number of medical ailments are treated or treatable through theapplication of electrical stimulation to an afflicted portion of apatient's body. Two examples of electrical stimulation may includemagnetic or inductive stimulation which may make use of a changingmagnetic field, and electric or capacitive stimulation in which anelectric field may be applied to the tissue. Neurons, muscle and tissuecells are all forms of biological circuitry capable of carryingelectrical signals and responding to electrical stimuli. For example,when an electrical conductor is passed through a magnetic field, anelectric field is induced causing current to flow in the conductor.Because various parts of the body also act as a conductor, when achanging magnetic field is applied to the portion of the body, anelectric field is created causing current to flow. In the context ofbiological tissue, for example, the resultant flow of electric currentstimulates the tissue by causing neurons in the tissue to depolarize.Also, in the context of muscles, for example, muscles associated withthe stimulated neurons contract. In essence, the flow of electricalcurrent allows the body to simulate typical and often desired chemicalreactions.

Electrical stimulation has many beneficial and therapeutic biologicaleffects. For example, the use of magnetic stimulation is effective inrehabilitating injured or paralyzed muscle groups. Another area in whichmagnetic stimulation is proving effective is treatment of the spine. Thespinal cord is difficult to access directly because vertebrae surroundit. Magnetic stimulation may be used to block the transmission of painvia nerves in the back (e.g., those responsible for lower back pain).Further, unlike the other medical processes that stimulate the body,electrical stimulation may be non-invasive. For example, using magneticfields to generate current in the body produces stimulation by passingthe magnetic field through the skin of a patient.

Magnetic stimulation also has proven effective in stimulating regions ofthe brain, which is composed predominantly of neurological tissue. Onearea of particular therapeutic interest is the treatment ofneuropsychiatric disorders. It is believed that more than 28 millionpeople in the United States alone suffer from some type ofneuropsychiatric disorder. These include specific conditions such asdepression, schizophrenia, mania, obsessive-compulsive disorder, panicdisorders, just to name a few. One particular condition, depression, isthe often referred to as the “common cold” of psychiatric disorders,believed to affect 19 million people in the United States alone, andpossibly 340 million people worldwide. Modern medicine offers depressionpatients a number of treatment options, including several classes ofanti-depressant medications like selective serotonin reuptake inhibitors(SSRI), MAIs, tricyclics, lithium, and electroconvulsive therapy (ECT).Yet many patients remain without satisfactory relief from the symptomsof depression. To date, ECT remains the “gold standard” of treatmentsfor severe depression; however, many patients will not undergo theprocedure because of its severe side effects.

Recently, repetitive transcranial magnetic stimulation (rTMS) has beenshown to have significant anti-depressant effects for patients, eventhose that do not respond to the traditional methods and medications. Inone embodiment of rTMS, a subconvulsive stimulation is applied to theprefrontal cortex in a repetitive manner, causing a depolarization ofcortical neuron membranes. The membranes are depolarized by theinduction of small electric fields, usually in excess of 1 volt percentimeter (V/cm). These small electric fields result from a rapidlychanging magnetic field applied non-invasively.

It is now well known to those skilled in the art that both the left andright prefrontal cortex regions of the brain have strong communicationlinks to Limbic System structures, which contain the “circuits”controlling mood and general behavior. One objective of rTMS is toprovide stimulation to these biological circuits through a non-invasive,sub-convulsive technique to relieve the symptoms of depression withoutmany of the negative side effects of ECT or medications. However, onereported side effect of rTMS for the treatment of depression is patientdiscomfort at the site of the stimulation. This discomfort is caused, inpart, by the depolarization of neuron membranes in the scalp and theresulting scalp muscle contractions that occur at the frequency of therTMS. Testing has shown that approximately 25% of rTMS patients reportthis discomfort to be at a level that is very uncomfortable. In general,the greater the power and the higher the frequency of the therapeuticmagnetic stimulation, the more discomfort is reported. Yet, reducing thepower levels may not be a viable option because greater power has beenshown to desirably stimulate deeper structures. Also, relatively higherfrequencies (e.g., greater than 1 Hertz (Hz)) have been shown to have agreater anti-depressant effect.

Therefore, it is desirable to develop techniques for reducing discomfortcaused by electrical stimulation.

SUMMARY OF THE INVENTION

The invention is directed to a novel method for reducing discomfortcaused by transcutaneous stimulation. The novel method includesproviding transcutaneous stimulation, reducing the transcutaneousstimulation at a first location, and substantially maintaining thetranscutaneous stimulation at a second location. The transcutaneousstimulation may be created by electric and/or magnetic fields. The firstlocation may be relatively proximate to the cutaneous surface and maycomprise tissue, nerves and muscle. Also, the second location may berelatively deeper than the first location and include, for example,brain tissue that requires the transcutaneous stimulation for treatmentpurposes. The invention further may include locating a conductor on atreatment area and/or a transcutaneous stimulation device relative tothe first location. In addition, the method may further includeadjusting how much the transcutaneous stimulation is reduced at thefirst location. Such adjusting of the transcutaneous stimulation may beaccomplished by applying a signal at the first location. The signal maybe inversely proportional to another signal used to create thetranscutaneous stimulation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating a technique for reducingdiscomfort caused by transcutaneous stimulation;

FIG. 2 is a block diagram illustrating another technique for reducingdiscomfort caused by transcutaneous stimulation;

FIG. 2A is a block diagram illustrating another technique for reducingdiscomfort caused by transcutaneous stimulation;

FIG. 3 is a block diagram illustrating another technique for reducingdiscomfort caused by transcutaneous stimulation;

FIG. 4 is a block diagram illustrating another technique for reducingdiscomfort caused by transcutaneous stimulation;

FIG. 5 is a block diagram illustrating another technique for reducingdiscomfort caused by transcutaneous stimulation;

FIG. 6 is a block diagram illustrating another technique for reducingdiscomfort caused by transcutaneous stimulation;

FIG. 7 is a block diagram illustrating another technique for reducingdiscomfort caused by transcutaneous stimulation;

FIG. 8 is a block diagram illustrating another technique for reducingdiscomfort caused by transcutaneous stimulation;

FIG. 9 is a flow diagram illustrating a technique for treating a patientusing transcutaneous stimulation;

FIG. 10 is a flow diagram illustrating a technique for treating apatient using transcutaneous stimulation;

FIGS. 11–18 illustrate additional possible conductor configurations forreducing discomfort caused by transcutaneous stimulation;

FIG. 19 provides an example of another possible conductor configurationfor reducing discomfort caused by transcutaneous stimulation;

FIGS. 20 and 21 illustrate an example configuration for the placement oftwo conductors for reducing discomfort caused by transcutaneousstimulation;

FIGS. 22A and 22B graphically depict the comparison of the electricfield created by a magnetic core device both with and withoutcancellation by the placement of two conductors for reducing discomfortcaused by transcutaneous stimulation; and

FIGS. 23 and 24 illustrate an embodiment with six conductors used toreduce the fields created by a magnetic core device for reducingdiscomfort caused by transcutaneous stimulation.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

Overview

In 1831, Michael Faraday discovered that the magnitude of an electricfield induced on a conductor is proportional to the rate of change ofmagnetic flux density that cuts across the conductor. Faraday's law,well known to those skilled in the art may be represented as E˜−(dB/dt),where E is the induced electric field in volts/meter, dB/dt is the timerate of change of magnetic flux density in Tesla/second. In other words,the amount of electric field induced in an object like a conductor isdetermined by two factors: the magnetic flux density and the time rateof change of the flux density. The greater the flux density and itsderivative, the greater the induced electric field and resulting currentdensity. Because the magnetic flux density decreases in strength as thesquare of the distance from the source of the magnetic field, the fluxdensity is greater the closer the conductor is to the source of themagnetic field. When the conductor is a coil, the current induced in thecoil by the electric field may be increased in proportion to the numberof turns of the coil.

When the electric field is induced in a conductor, the electric fieldcreates a corresponding current flow in the conductor. The current flowis in the same direction of the electric field vector at a given point.The peak electric field occurs when dB/dt is the greatest and diminishesat other times. If the electric field decreases, for example after amagnetic pulse, the current flows in a direction that tends to preservethe electric field (i.e., Lenz's Law).

In the context of electrical stimulation of the anatomy, certain partsof the anatomy (e.g., nerves, tissue, muscle, brain) act as a conductorand carry electric current when an electric field is presented. Theelectric field may be presented to these parts of the anatomytranscutaneously by applying a time varying (e.g., pulsed) magneticfield to the portion of the body. For example, in the context of TMS, atime-varying magnetic field may be applied across the skull to create anelectric field in the brain tissue, which produces a current. If theinduced current is of sufficient density, neuron membrane potential maybe reduced to the extent that the membrane sodium channels open and anaction potential response is created. An impulse of current is thenpropagated along the axon membrane which transmits information to otherneurons via modulation of neurotransmitters. Such magnetic stimulationhas been shown to acutely affect glucose metabolism and local blood flowin cortical tissue. In the case of major depressive disorder,neurotransmitter dysregulation and abnormal glucose metabolism in theprefrontal cortex and the connected limbic structures may be a likelypathophysiology. Repeated application of magnetic stimulation to theprefrontal cortex may produce chronic changes in neurotransmitterconcentrations and metabolism so that depression is alleviated.

Systems and Methods of Reducing Discomfort

FIG. 1 is a block diagram illustrating a technique for reducingdiscomfort caused by electrical stimulation. As shown in FIG. 1, asystem 100 includes a magnet stimulation circuit 101. Magnet stimulationcircuit 101 is an electric circuit that provides a power signal to amain magnet (not shown). The power signal may be any time-varyingelectric signal capable of generating an electric and/or magnetic field.The main magnet may be used to conduct transcranial magnetic stimulation(TMS) and/or repetitive transcranial magnetic stimulation (rTMS) asdescribed in U.S. Pat. Nos. 5,725,471, 6,132,361 6,086,525 and6,425,852, and incorporated herein by reference.

In the following description, for purposes of explanation and notlimitation, specific details are set forth regarding system 100 andother systems, methods and techniques for reducing discomfort caused byelectric stimulation. For example, particular components, componentconfigurations and placements, devices, techniques, etc. are describedin detail. However, it should be appreciated that the invention is notmeant to be limited to these examples. The examples, components, etc.are provided simply to provide an understanding of the invention. Itwill be apparent to one skilled in the art that the invention may bepracticed in other embodiments that depart from these specific details.Detailed descriptions of well-known devices, components, techniques,etc. are omitted so as not to obscure the description of the invention.

System 100 includes an inductive device 102. Inductive device 102operates to receive a current induced upon it by a wire 107 that carriesa current (I) in magnet stimulation circuit 101. The current induced oninductive device 102 by wire 107 is proportional to the time derivativeof the current (I) in magnet stimulation circuit 101, based onprinciples of electrical induction well known to those skilled in theart. Inductive device 102 may be any device that is capable of having acurrent induced thereon, including for example a coil of wire and/or acurrent transformer, well known to those skilled in the art. Inductivedevice 102 may be in communication with an amplifier 103. Amplifier 103is in communication with a signal processor 104. Signal processor 104 isin communication with a series of conductors 105 a–e. Conductors 105 maybe small electrodes, having small cross section so as to minimizeheating from induced eddy currents. Typical maximum dimension may beapproximately 5 mm. The shape of the electrodes is determined by thegeometry of the electric field induced in the surface tissue. When inuse, the electrodes are in electrical contact with the surface tissue,typically through a conductive gel which reduces the contact impedanceto less than approximately 20 kOhms. Also, conductors 105 may be affixedto a flexible circuit pad 106.

Flexible circuit pad 106 may be made of a Mylar™, polyester, or otherpolymer-type material that permits the pad and thus conductors 105 tofit the contours of the treatment area on the patient and/or to fit thecontours of the magnetic stimulation device (e.g., magnet withferromagnetic core). Flexible circuit pad 106 also may have an adhesivematerial that permits the pad, and therefore conductors 105, to beaffixed to a location in which system 100 is to operate. Also, flexiblecircuit pad 106 may have a conductive gel that facilitates conduction ofelectrical energy between conductors 105 and the treatment area. Theconductive gel may be covered with a removable paper or plastic seal(not shown), which when removed permits the conductive gel to come intocontact with the treatment area.

Flexible circuit pad 106 may include a connector that permits componentsof system 100 (e.g., signal processor 104) to be readily attached anddisconnected therefrom. In addition, flexible circuit pad 106 may havecertain insulating materials to prevent undesirable conducting ofelectrical energy with the patient and/or with components of system 100.

Flexible circuit pad 106 also may include electrical or physicaldisposal mechanisms that require a new flexible circuit pad to be usedwith each treatment. Alternatively, the disposal mechanism may allow acertain flexible circuit pad a certain number of times and/or be used bya certain patient. Therefore, the disposal mechanism may prohibitundesirable re-usage of the flexible circuit pad 106, and thereforefacilitate sanitary usage of flexible circuit pad 106 both for anindividual patient and across numerous patients.

In operation, when main stimulation circuit 101 is provided power froman external power source (not shown) to conduct proper stimulation ofthe patient, current (I) travels through main stimulation circuit 101.Main stimulation circuit 101 is connected to a magnetic stimulationdevice (e.g., an electromagnet) (not shown) that creates a magneticfield or fields designed to provide treatment to a particular area onthe patient. As shown in FIG. 1, providing power to the magneticstimulation device creates magnetic fields 108 a–f.

As discussed in U.S. Pat. Nos. 5,725,471, 6,132,361 6,086,525 and6,425,852, incorporated herein by reference, magnetic fields 108 a–f actto stimulate nerves, tissue and muscle etc. in the patient for treatmentor therapeutic purposes. Current (I) travels through magneticstimulation circuit 101 and onto inductive device 102 via wire 107. Itshould be appreciated that inductive device 102 may be located in serieswith and/or in parallel with main stimulation circuit 101, or in anyelectrical direct or indirect communication configuration.

Inductive device 102 operates to sense a current (I) provided to magnetstimulation circuit 101 by receiving an induced electrical value that isbased on the current (I) that passes to the magnetic stimulation circuit101. For example, the value received by inductive device 102 may be aninduced voltage that is proportional to a change in current (I) inamperes divided by the amount of time in which the change in currenttakes place. This is expressed mathematically as E=L di/dt, where E isthe induced voltage, di is the change of current, dt is the amount oftime in which the change in current takes place, and L represents theelectrical inductive properties of the inductive device 102. In oneembodiment, the induced voltage, for example, may then be provided to anamplifier 103. Amplifier 103 operates to manipulate (e.g., boost) theinduced voltage E as required by system 100 and by signal processor 104.

Signal processor 104 receives the amplified induced voltage signal fromamplifier 103 and may operate to further manipulate the signal dependingon the characteristics of system 100. For example, signal processor 104may operate to invert a polarity of the signal from amplifier 103. Inthis way, the magnetic and/or electric fields created by the magneticstimulation device are in substantially opposite polarity to themagnetic and/or electric fields created by conductors 105.

Also, signal processor 104 may operate to ensure that the timing of thefields created by magnetic stimulation device and conductors 105 aregenerated substantially simultaneously. In particular, because signalprocessor 104 receives a signal from the circuitry that powers themagnetic stimulation device, signal processor 104 may operate to “gate”or activate the signal to conductors 105 at the same time the magneticstimulation device is gated. In this way, the fields from the magneticstimulation device are present at substantially the same time that thefields from conductors 105 are present. Synchronizing the fields mayfurther facilitate the ability of the fields from conductors 105eliminating or reducing the undesirable effects of the fields from themagnetic stimulation device.

Therefore, amplifier 103 and/or signal processor 104 further facilitatethe cancellation of the fields from the magnetic stimulation device andconductors 105, as desired (e.g., at or near the scalp of a rTMSpatient). The precise manipulation of the signal by signal processor 104and/or amplifier 103 will depend upon many variables including thephysical and electrical characteristics of system 100, of the patientand the treatment area, and of conductors 105, just to name a few. Byreceiving the signal from amplifier 103 and by understanding thecharacteristics of the other variables, signal processor 104 may beadapted to provide the proper signal timing and strength to conductors105 so as to create the proper fields, at the proper time, in the properlocation.

In just one embodiment in the context of rTMS or TMS, the stimulatingmagnet may be applied to a certain location on the patient's head so asto determine the minimum amount of induced current required to affectthe particular patient's neurons. For example, the “test” location maybe the patient's motor center as the results are easy to identifybecause a portion of the patient's body may move in response to theappropriate dosage. Once the proper dose is determined at the motorcenter, the stimulating magnet with attached flexible circuit pad 106may be placed on the particular treatment location to affect the neuronsrequired to treat the patient's depression.

Signal processor 104 may then provide the signal (e.g., a time-varyingsignal) to conductors 105. Providing the signal to conductors 105 causesa current to flow in conductors 105, which in turn creates an electricfield that is generated proximate to each of the conductors. Thiselectric field may be used to offset the electric and magnetic fieldscreated by the magnetic stimulation device that create discomfort in thepatient, without adversely impacting the desired therapeutic effect ofthose magnetic fields. For example, in the context of rTMS or TMS, theelectric and/or magnetic fields created by conductors 105 may bedesigned to eliminate and/or reduce the magnetic fields created by themagnetic stimulation device at the surface of the scalp that creatediscomfort in the patient, without reducing the efficacy of the magneticfield created by the magnetic stimulation device within the area that isdesired to be treated (e.g., the brain).

In order to ensure that the magnetic fields created by conductors 105reduce the discomfort to the patient without diminishing the usefulnessof the treatment, certain characteristics of system 100 may be varied.Although not meant to be exclusive such variances may include modifyingthe electrical characteristics (e.g., conductivity) and physicalcharacteristics (e.g., surface area) of conductors 105. Signal processor104 may be designed to scale the applied voltage signal up and/or downto a level that permits conductors 105 to reduce the discomfort causedby the magnetic stimulation device on the patient. Also, amplifier 103may be designed to amplify the induced voltage signal up and/or down. Itshould be appreciated that system 100 may include any combination ofvarying the above-mentioned characteristics.

In addition to being dependent on the characteristics of system 100, howmuch and which system features vary may depend on the particularcharacteristics of the patient. For example, in the context of rTMS orTMS, such specific characteristics may include, but not be limited to,the shape and size of the patient's head, the amount and density of hairon the patient's head, the particular area of the cranium that isdesired to be treated, etc.

FIG. 2 is a block diagram illustrating another technique for reducingdiscomfort caused by electrical stimulation. As shown in FIG. 2, asystem 200 includes a flexible circuit pad 106 having a number ofconductors 202 a–e. Flexible circuit pad 106 may have an adhesivematerial that permits the pad, and therefore the conductors, to beaffixed to a location in which system 200 is to operate. Conductors 202may be small electrodes, having a maximum dimension of approximately 5mm. Also, conductors may vary in their electrical characteristics (e.g,conductivity) and physical characteristics (e.g., size and shape)depending on their placement on flexible circuit pad 106 relative to thearea that is being treated on the patient. Each of conductors 202 may bein communication with one or more pickup loops 204 via one or more wires205 a–f. Also, conductors 202 may have another connection to one or morepickup loops 204 via one or more wires 206. In these instances, wire 206may be used to create a voltage potential or voltage difference onconductors 202. Also, wire 206 may be connected to a ground potential(either separately or grounded to the patient under treatment) to createthe voltage difference. The voltage potential created on each ofconductors 202 creates a desired electric field. Although just one wire206 is shown in FIG. 2 for the purpose of clarity, it should beappreciated that each of conductors 202 may have a similar voltagereference connection attached thereto.

Pickup loop 204 may be any conductive material having any particularshape (e.g., straight wire, looped coil, etc.). Also, wires 205 a–f maybe any conductive material capable of carrying an electrical signal frompickup loop 204 to conductors 202. Pickup loop 204 and wires 205 may bean integrated part of flexible circuit pad 106. Also, pickup loop 204and wires 205 may be individual components independent of flexiblecircuit pad 106 that may be moved in various treatment locations duringoperation.

As discussed with reference to FIG. 1, a current (I) is applied to amagnetic stimulation device (not shown) to produce a pulsed magneticfield (having a flux density B) that is designed to provide medicaltreatment (e.g., TMS) to a patient. In operation, pickup loop 204 may beplaced anywhere within or in close proximity to the pulsed magneticfield or in a similar magnetic field that is proportional to thetherapeutic field. The therapeutic field induces an electric field (E1)in the surface tissue whose lines of flux are shown as 203 a–f. Thiselectric field, E1, is proportional to dB/dt. The magnetic field fluxlines (B) are orthogonal to these electric field lines.

The pickup loop may be connected via conductors 205 directly (orindirectly) between an electrode (202 a–e) and a ground reference pointor a second electrode. As the magnetic field crosses pickup loop 204, acurrent is generated in pickup loop 204 and a voltage may be establishedbetween the connected electrodes that is generally proportional to−dB/dt and −dI/dt over certain regions near the electrodes. This voltagecreates a proportionate electric field (E2) in the surface tissuebetween the electrodes. Since this applied electric field (E2) may bedesigned to be inversely proportional to the induced electric field(E1), there is subtraction wherever the fields superimpose which resultsin the desired reduction of discomfort.

In order to effectively distribute the canceling electric field (E2)multiple electrodes may be used. In this case, the voltage generated bypickup loop 204, which is proportional to the magnetic field created bythe magnetic stimulation device, may be provided to each of conductors202 via wires 205. As a result, voltages may be established between theseveral conductors 202 and creating corresponding electric fieldsbetween each of conductors 202. The electric fields created byconductors 202 are designed such that the undesired stimulation of thepatient (e.g., in the scalp) is reduced, but the desired stimulation(e.g., in the brain) created by the magnetic stimulation device'smagnetic field is not compromised. For example, in the context oftranscranial magnetic stimulation, the electric fields created byconductors 202 may operate to reduce the impact of the magneticstimulation device's magnetic field close to the surface of the scalp,while allowing the electromagnet's magnetic fields to penetrate deeperwithin the head and desirably stimulate the brain.

The desired strength and location of the fields created by conductors202 may be varied depending on the characteristics of the patient and ofsystem 200, as previously discussed. Although not exclusive of thetechniques for varying the strength and location of the electric fieldscreated by conductors 202, the electric fields may be varied bymodifying the number of turns, the cross-sectional area of pickup loop204, or by interposing an amplification device (e.g., transformer)between the pickup loop and the electrodes as described by System 300,FIG. 3. Another technique for varying the electric field strengthcreated by conductors 202 includes using more than one pickup loop andvarying the location of pickup loop(s) with respect to the magneticfield.

By sensing the strength of the magnetic field created by the magneticstimulation device, pickup loop 204 may create fields (via communicationwith conductors 202) that are able to eliminate or reduce undesiredeffects of the magnetic stimulation device, while permitting the desiredtherapeutic effect of magnetic stimulation device (e.g., TMS). Theprecise size and location of the fields created by conductors 202 may bedetermined by vectorally adding, as is well known to those skilled inthe art, the corresponding fields created by conductors 202 and by themagnetic stimulation device.

FIG. 2A is a block diagram illustrating another technique for reducingdiscomfort caused by electrical stimulation. Specifically, FIG. 2A showsanother configuration of pickup coils and conductor placement, ascompared to that shown in FIG. 2. As shown in FIG. 2A, conductors 209a–f are distributed on flexible circuit pad 106. Conductors 209 also arein communication with pickup coils 210 a–d. Wires 207 a–d are connectedfrom conductor 209 to pickup coils 210 a–d, respectively. Also, pickupcoils 210 a–d are connected to a voltage reference point (e.g., groundreference) via wires 208 a–d, respectively. The voltage reference may beseparately provided, provided as part of the flexible circuit pad and/orbe provided via attachment to the patient under treatment.

In operation, each of pickup coils 210 provides a certain predeterminedvoltage value to each of its respective conductors 209. The precisevoltage value provided by pickup coils 210 to conductors 209 may bebased on the electric and/or magnetic field that is desired to becreated by each of conductors 209 to offset the undesirable effects ofthe magnetic stimulation device (not shown). The design of the voltagevalue may be made to vary depending on the size and construction ofconductors 209, as well as the size and construction of pickup coils210. For example, possible voltage values are indicated in FIG. 2A.These voltage values are merely provided for the purpose of example andto provide further the explanation.

In just one embodiment, for example, pickup coil 210 d may provide −2volts to each of conductors 209 e and 209 f. Also, pickup coil 210 c mayprovide −1 volt to conductor 209, while pickup coil 210 b provides +1volt to conductor 209 c. Conductors 209 a and 209 b may each receive +2volts from pickup coil 210 a. The voltage values and the polarity of thevoltage may be based on the electric and/or magnetic field that isdesired to be created on each of conductors 209. For example, a highervoltage value (e.g., 5 volts) may be applied to conductors 209 c and 209d in recognition that greater undesirable field strengths are created bythe magnetic stimulation device at that location. Also, by establishinga similar voltage but different polarity conductors may work in tandem(e.g., 209 a and b, 209 c and d, and 209 e and f) to create the desiredfields.

Although not shown in FIG. 2A, it should be appreciated that a voltagepotential may be created individually on each of conductors 209. Inparticular, a voltage potential (e.g., ground potential) may created onone or more conductors 209 to generate a desired field. Also, it shouldbe appreciated that the number of coils 210 and conductors 209 may varydepending upon the particular application.

FIG. 3 is a block diagram illustrating another technique for reducingdiscomfort caused by electrical stimulation. As shown in FIG. 3, asystem 300 is similar to system 200, discussed with reference to FIG. 2.In addition to the components shown in system 200, system 300 alsoincludes a signal processor 301 in communication with pickup loop 204via wire 302. As with signal processor 104, discussed with reference toFIG. 1, signal processor 301 may operate to manipulate the electricalvoltage and/or current induced on pickup loop 204 and provided toconductors 202. In particular, depending on the characteristics ofsystem 300, signal processor 301 may be designed to scale the inducedvoltage and/or current signal up and/or down to a level that permitsconductors 205 to create a magnetic field sufficient to reduce thediscomfort caused by the magnetic stimulation device (not shown) on thepatient, without reducing its therapeutic effects.

The design and output of signal processor 301 may be used in lieu of orin combination with the modifications used to vary the electric fieldscreated by conductors 202, as discussed with reference to FIG. 2 withregard to the characteristics of pickup loop 204. An amplifier (notshown), similar to amplifier 103 discussed with reference to FIG. 1 maybe designed to amplify the induced voltage signal up and/or down incombination with signal processor 301. Also, system 300 may include anycombination of varying the above-mentioned characteristics to allowconductors 202 to produce electric fields that have propercharacteristics to reduce discomfort created by therapeutic electricalstimulation. For example, having the flexibility to vary the signal frompickup loop 204 using signal processor 301 may allow less stringentdesign criteria restrictions for the construction and placement ofconductors 202, and thus further facilitate on-site implementation.

Also, it should be appreciated that signal processor 301 may be designedto allow different voltage and/or current signal strengths to be appliedindividually to each of conductors 202. This variable conductor signalmay be desirable in certain configurations. For example, as shown inFIG. 3, electric field lines 203 a and 203 d converge as they approachthe center of flexible circuit pad 106. Because it is well known tothose skilled in the art that field lines 203 a and 203 d may vectorallyadd in this location, resulting in a greater electric field strength(created by the magnetic stimulation device) at this location than atother locations in system 300.

In the context of rTMS and/or TMS, this greater electric field strengthbeneficially may result in ideal stimulation of the brain for thetreatment of depression, for example. At the same time, this greaterelectric field strength also undesirably may result in creating greaterdiscomfort in the non-brain tissue, muscle and/or nerves, or other partsof the brain that do not need to be stimulated. Therefore, in order tooffset the undesirable effect where electric field lines 203 a and 203 dare stronger, signal processor 301 may apply a larger voltage and/orcurrent signal to a conductor located in this location than to otherconductors. For example, conductor 202 c may receive a greater voltageand/or current signal than the other conductors because it is located inthe area where electric field lines 203 a and 203 d are stronger.Therefore, signal processor 301 may permit conductor 202 c to create arelatively greater electric field as compared to the other conductors.

Although the discussion of the ability of signal processor 301 to varythe current and/or voltage signal provided to each of conductors 202 hasbeen discussed in the context of field strength, this example is notexclusive. It should be appreciated that other factors may drive thedecision to provide different signals to each of conductors 202. Forexample, the anatomy or sensitivity of the part of the patient that isbeing treated with respect to the arrangement of the conductors onflexible circuit pad 106 may result in signal processor 301 providing arelatively greater and/or lesser current to conductor 202 a than theother conductors. Also, as another example, the lines of flux created bythe main electromagnet device may be different than as illustrated inFIG. 3 and thus the design of signal processor 301 may be such thatgreater current and/or voltage signal may be provided to other ofconductors 202. Therefore, it should be appreciated that the discussionis not meant to be limited to any of the above examples, which simplyare provided for the purpose of clarity and explanation.

FIG. 4 is a block diagram illustrating another technique for reducingdiscomfort caused by electrical stimulation. As shown in FIG. 4, asystem 400 includes a flexible circuit pad 401 having conductors 402a–d. Although conductors 402 are shown centered and evenly spaced onflexible circuit pad 401, it should be appreciated that conductors maybe any size or shape, arranged in any configuration, and placed on anylocation on flexible circuit pad 401. Also, although conductors 402 areillustrated as having an arc shape, it should be appreciated that theinvention is not limited to any particularly shaped conductors. Forexample, conductors 402 may have any shape, including the shapesdepicted in FIGS. 1–3, circular coil shapes, etc. Conductors 402 alsoare connected to a common connector 403. Common connector 403 mayprovide a referenced voltage level, like a ground voltage level, forexample. Also, as previously discussed, the magnetic stimulation device(not shown) creates magnetic flux lines 404 a–f

In operation, system 400 uses shielding techniques to reduce and/or toredistribute the electric field effects of fields 404 a–f created by themagnetic stimulation device and used for therapeutic purposes (e.g.,rTMS and TMS). In particular, as previously discussed, magnetic fluxlines 404 create electric fields which induce electrical currents in thenerves, muscle and tissue of the patient. Certain of these nerves,muscle and tissue may be desirably stimulated by the induced current(e.g., the brain in rTMS and TMS). However, certain of other nerves,muscle and tissue (e.g., the scalp in rTMS and TMS) may be undesirablystimulated by the induced current created by the magnetic stimulationdevice.

Conductors 402 operate to disrupt the flow of current in the patient'ssurface tissue so that system 400 may permit the desirable stimulationof certain parts of the patient's anatomy, while reducing or eliminatingthe undesirable stimulation of other parts of the patient. Inparticular, conductors 402 may be designed with certain physical and/orelectrical characteristics such that they offer a path of lesserresistance for the induced current than the portion of the patient inwhich the undesired induced current would flow. As a result, conductors402 operate to reduce or eliminate the undesired current induced acertain portion of the patient, while still permitting the desiredcurrent to be induced in another portion of the patient.

The characteristics of conductors 402 may be designed to provide thepath of lesser resistance based upon a number of factors and variables.For example, increasing the conductivity of conductors 402 may beaccomplished by varying the physical and/or electrical characteristicsof conductors 402 as compared to the particular portion of the patientthat is being treated. Also, the shape and configuration of conductors402 relative to the direction and strength of magnetic fields 404 a–fmay be varied (e.g., conductors 402 may be curved as illustrated in FIG.4) to allow conductors 402 to provide a larger conductive path of lesserresistance. In addition, conductors 402 may be configured and shaped(e.g., curved) to allow the conductors to be in a substantiallyperpendicular arrangement with respect to electric field lines 404 a–fin order to “intercept” more of the current caused by the inducedelectric field, conduct the intercepted current to a more acceptablelocation, and redistribute the current back to the surface-proximatetissue in a manner that minimizes sensation. Although determining theconfiguration and shape of conductors 402 may be necessary in properlyreducing or eliminate the undesired induced current on the patient, itshould be appreciated that the invention is not limited to anyparticular shape or configuration of the conductors, but include allpossible shapes and configurations.

In the context of rTMS and TMS, conductors 402 may have electrical andphysical characteristics to redirect the flow of current away from thetissue, nerve, and muscle found closer to the surface of the head orscalp. One way of accomplishing this may be by determining the typicalor specific electrical conductivity of the surface-proximate tissue,nerve, and muscle, and designing conductors 402 to have an equal orgreater conductivity, as necessary. Also, the electrical and physicalcharacteristics of conductors 402 may be designed to redirect currentthat may stimulate the surface-proximate tissue, nerve, and musclewithout significantly interfering with the therapeutic current desirablyinduced on the brain tissue under treatment.

Although conductors 402 are shown connected to common connector 403, itshould be appreciated that any one or more of conductors 402 may operateindependently of the others, or that just one conductor may be used. Forexample, in the context of rTMS and TMS, it is well known to thoseskilled in the art that the trigeminal nerve is particularly sensitiveto electrical stimulation as compared to other prefrontal areas of thescalp. Therefore, one or more conductors 402 may operate together orindependently in close proximity to the trigeminal nerve to redirect anynearby electric fields. Also, certain conductors 402 may be dedicated toprotecting the trigeminal nerve specifically. In addition, in thecontext of the trigeminal nerve, in just one embodiment, the conductoror conductors 402 may be positioned directly over the trigeminal nerveand attached directly to the patient in a direction consistent with thedirection of the nerve. In this way, the arrangement, positioning andconfiguration of the conductor or conductors may be customized tolocally protect a particular tissue, muscle or nerve, like thetrigeminal nerve. Although the discussion has focused on protecting ofthe trigeminal nerve, it should be appreciated that one or moreconductors may be placed over any part of the patient that may be moreor less sensitive or that simply is desired to be protected. Inaddition, it should be appreciated that placing one or more conductorson the patient may be used in combination with any of the othertechniques described with reference to FIGS. 1–3.

FIG. 5 is a block diagram illustrating another technique for reducingdiscomfort caused by electrical stimulation. As shown in FIG. 5, asystem 500 includes conductive coils 503 a and 503 b located above apatient's head 502 and under a magnetic stimulation device 501 (e.g.,magnet with ferromagnetic core). Also, conductive coils 503 a and 503 bare in communication with a signal processor 506, which receiveselectrical power from a power source 507. Although the arrangement ofmagnetic stimulation device 501 and conductive coils 503 a and 503 b areillustrated in FIG. 5 in a certain configuration with respect to thepatient's head 502, it should be appreciated that this configuration isnot meant to be exclusive, but simply provide one example for thepurposes of clarity and explanation. For example, conductive coils 503 aand 503 b may be in direct or indirect contact with either the patient'shead 502 and/or magnetic stimulation device 501. Furthermore, conductivecoils 503 a and 503 b may be located other than in between the patient'shead 502 and magnetic stimulation device 501. Also, although magneticstimulation device 501 is shown as a magnet having an arc-shapedferromagnetic core, it should be appreciated that it may include anydevice capable of creating magnetic stimulation.

When an electric voltage and/or current is applied to magneticstimulation device 501, a magnetic field having magnetic flux lines 505a–d is created between the poles of magnetic stimulation device 501. Thepulsed magnetic field created by magnetic stimulation device 501 andhaving magnetic flux lines 505 a–d also create an electric fieldrepresented by 504 a–e. Of course, as with FIGS. 1–4 the depiction ofmagnetic flux lines 505 a–d and electric field 504 a–e are merelyrepresentative of such properties simply for the purpose of a discussionin the context of the invention.

As shown in FIG. 5, electric fields 504 a–e become dispersed as theymove away from magnetic stimulation device 501. Yet, at the top of thepatient's head 502 (or perhaps in another location depending on thelocation and configuration of the magnetic stimulation device) locatedbetween the poles of magnetic stimulation device 501, the electric fieldlines 504 a–e are located closer to one another. Also, well known tothose skilled in the art, the strength of the electric field decreasesas a square of the distance away from the source of the electric field.These two well-known properties of electric fields create a relativelystronger electric field presence at the top of the patient's head 502and between the poles of magnetic stimulation device 501. As a result,this relatively stronger electric field in turn induces a relativelylarger current in the surface-proximate tissue, muscle and nerveslocated at the top of the patient's head 502. In some instances, thisrelatively larger current may cause greater discomfort to certainportions of the patient's anatomy (e.g., the scalp). System 500 usesconductive coils 503 a and 503 b to help alleviate the patient'sdiscomfort.

Conductive coils 503 a and 503 b receive electrical power from powersource 507 via signal processor 506. When conductive coils 503 a and 503b receive electrical energy another magnetic field (B2, not shown) iscreated by conductive coils 503 a and 503 b. The magnetic field (B2)created by conductive coil (in cooperation with power source 507 andsignal processor 506) may be designed to reduce, eliminate or counteractthe magnetic lines of flux 504 a–e, so as to eliminate discomfort causedby the current induced in a portion of the patient's head 502 byelectric field 504 a–e and magnetic lines of flux 505 a–d. The location,size and strength of conductive coil's 503 magnetic field (B2) requiredto sufficiently offset the surface effect of the magnetic field (B)created by magnetic stimulation device 501 may vary with the particularcircumstances and construction of system 500. For example, the necessaryoffsetting magnetic field (B2) created by conductive coils 503 a and 503b may vary with the patient, the construction and location of magneticstimulation device 501, the size and construction of conductive coils503 a and 503 b, and other variable circumstances. Also, conductivecoils 503 a and 503 b may be wound in a direction opposite of mainmagnetic stimulation device.

There are numerous methods and techniques available to accommodate thevariation necessary in system 500 to sufficiently offset the undesirableeffect of the fields created by magnetic stimulation device 501. Forexample, signal processor 506 may receive a feedback signal (not shown)from magnetic stimulation device 501 and/or its electric or magneticfields so as to create a properly sized magnetic field from conductivecoils 503 a and 503 b. This feedback may be provided via a directconnection to magnetic stimulation device 501 or by receiving a currentsupplied to magnetic stimulation device 501. Using this input, signalprocessor 506 may vary the level of power provided to conductive coils503 a and 503 b and thus vary its resulting and offsetting fields. Analternative arrangement is to permit the operator to manually adjustcurrent levels to coils 503 a and 503 b based on patient feedback, basedon other signal feedback, or arbitrarily.

Also, the arrangement, location and configuration of may be varieddepending on the particular circumstances. For example, the number ofturns or loops in conductive coils 503 a and 503 b may be varied basedon the output of magnetic stimulation device 501. Also, as depicted inFIG. 5, a plane of conductive coils 503 a and 503 b may be orthogonal tothe magnetic field created by the magnetic stimulation device 501 and/orto magnetic stimulation device 501 itself. In addition, conductive coils503 a and 503 b may be designed to have a certain cross-sectional areaand/or aspect ratio.

Also, although signal processor 506 and power source 507 are shown, thesize and construction of conductive coils 503 a and 503 b may bedesigned such that the desired strength of the magnetic field is createdby conductive coils 503 a and 503 b itself. This design may be based onthe electrical properties of conductive coils 503 a and 503 b, such asconductivity, field saturation level, influence of magnetic flux lines504 a–e on conductive coils 503 a and 503 b, and undesirable heatgenerating properties of conductive coils 503 a and 503 b, etc. Theconductive coils may have air cores, or ferromagnetic cores of materialssuch as 3% silicon steel or vanadium permandur. These are just examplesof possible materials that may be used to create conductive coils 503 aand 503 b.

It should be appreciated that the described techniques for arriving atthe correct offsetting magnetic field created by conductive coils 503 aand 503 b may be accomplished via a combination of these or any othertechniques. Also, it should be appreciated that the size and location ofthe countervailing magnetic field created by conductive coils 503 a and503 b may be such that the discomfort causing effect onsurface-proximate tissue, muscles and nerves are reduced, while thetherapeutic effect of magnetic lines of flux 505 a–d on deeper elements(e.g., the brain) are not adversely effected. For example, the geometryof conductive coils 503 a and 503 b may be varied such that its magneticfields do not deeply penetrate the patient (e.g., air core coil). Asanother example, the current provided to conductive coils 503 a and 503b may be minimized so as to produce relatively weaker magnetic fields.

It also should be appreciated that conductive coils 503 a and 503 b maybe one of an array of coils. In this example, each of the coils may havesimilar or different physical and electrical characteristics dependingupon the portion of magnetic stimulation device's 501 magnetic fieldthat it is designed to be operated upon. In addition, each coil of suchan array may have a separately adjustable current drive level that isset by the signal processor 506 based on preset values, empiricallydetermined values, sensed feedback, patient feedback to the operator, orindependent manual setting by the operator.

The coils may be attached directly or indirectly to the patient's head502 and/or attached directly or indirectly to magnetic stimulationdevice 501. System 500 also may use shielding techniques to block orreduce the magnetic fields generated by conductive coils 503 a and 503 bfrom adversely effecting the operation of ferromagnetic core 501, or tominimize coupling of the stimulator field (B) with the conductive coils.For example, system 500 may include a magnetic shield (not shown) placedin some location proximate and/or between conductive coils 503 a and 503b and magnetic stimulation device 501, so as to reduce or eliminate themagnetic field between conductive coils 503 a and 503 b and the magneticstimulation device 501. Such magnetic shields may be fabricated fromferrite materials, as an example.

The components shown in FIG. 5 are not exclusive but are provided simplyfor the purposes of explanation. Other components may be desirable, aswell. For example, communication between conductive coils 503 a and 503b may pass through a shunting device, so as to eliminate any undesirableconduction of energy back into signal processor 506.

FIG. 6 is a block diagram illustrating another technique for reducingdiscomfort caused by electrical stimulation. As shown in FIG. 6, asystem 600 includes one or more ferrite pads 601 located above apatient's head 502 and under a magnetic stimulation device 501. Itshould be appreciated that the physical configuration of ferrite pads601 are illustrated for the purpose of discussion and clarity, and isnot meant to be an exclusive representation of such a configuration. Forexample, as with conductive coils 503 a and 503 b discussed withreference to FIG. 5, ferrite pads 601 may be located between magneticstimulation device 501 and the patient's head 502. Also, as discussed,ferrite pads 601 may be attached directly and/or indirectly to thepatient's head 502 and/or directly or indirectly connected to magneticstimulation device 501. In addition, the number and placement of ferritepads 601 are not limited to any particular configuration, and may beused in conjunction with any of the other methods described herein.

Ferrite pads 601 operate to effectively “absorb” the magnetic field andmagnetic flux lines 504 a–e created by magnetic stimulation device 501.In particular, ferrite pads 601 may be designed and constructed tooffset, reduce and/or absorb the magnetic flux lines 504 a–e thatstimulate the surface-proximate tissue, while permitting those magneticflux lines that penetrate deeper into the patient for therapeuticpurposes to pass substantially unaffected. Also, by using a ferritematerial, ferrite pads 601 typically have low conductivity and thereforedo not encourage induced eddy currents and associated heating ortemporal disruption of the therapeutic magnetic field created bymagnetic stimulation device 501. It should be appreciated that althoughsystem 600 has been described in the context of ferrite material, thepads also may be made of other non-ferrite material and/or a combinationof ferrite material and non-ferrite materials.

The components shown in FIG. 6 are not exclusive but are provided simplyfor the purposes of explanation. Other components may be desirable, aswell. For example, in response to the magnetic field from the magneticstimulation device 501, ferrite pads 601 may create fields thatundesirably are directed toward magnetic stimulation device 501. Suchundesirable fields may effect the operation and/or efficiency ofmagnetic stimulation device 501. For example, such fields may causemagnetic stimulation device 501 to saturate at a different level thanexpected. Therefore, other components may be used to block or attenuatethe fields from ferrite pads 601 to magnetic stimulation device 501.Such blocking techniques may be designed to be unilateral orsubstantially unilateral to permit the fields to pass from magneticstimulation device 501 to ferrite pads 601, but to interrupt the fieldsfrom ferrite pads to magnetic stimulation device 501.

FIG. 7 is a block diagram illustrating another technique for reducingdiscomfort caused by electrical stimulation. As shown in FIG. 7, asystem 700 includes a magnetic stimulation device 702 that receivespower from a stimulation circuit 703 to create magnetic fields (notshown) in the patient's head 706. As previously discussed, magneticstimulation device 702 creates magnetic fields that induce currentwithin the patient for certain beneficial therapeutic effects, like thetreatment of depression using TMS, for example. Also, however, the samemagnetic fields create discomfort for the patient by undesirablyinducing current into surface-proximate tissue, nerves and muscle.

A surface coil 701, located at or near the patient (and possibly betweenthe patient and magnetic stimulation device 702), may be used to offset,eliminate or reduce the undesired effects of the magnetic fields createdby magnetic stimulation device 702. In particular, surface coil 701 maygenerate its own magnetic field(s) that offset the portion of themagnetic fields created by magnetic stimulation device 702 that act toundesirably stimulate surface-proximate tissue, nerves and muscle. Also,the values of the magnetic fields created by surface coil 701 may besuch that the magnetic fields created by magnetic stimulation device 702having therapeutic value continued to be passed to the patient withoutsubstantial interference.

The strength and timing of the magnetic fields, for example, created bysurface coil 701 may be generated using a number of techniques. Thesetechniques are similar to the example discussed with reference to FIGS.1–4. Although these techniques will be discussed, it should beappreciated that these examples are provide for the purpose of clarityand further explanation, but are not meant to provide exclusive examplesas contemplated by the invention.

In one embodiment, for example, power source 705 provides power tosignal generator 704. Signal generator 704 then passes a signal (e.g.,current and/or voltage signal) to surface coil 701 to create a magneticfield from surface coil 701. The required strength and location of themagnetic field from surface coil 701 may be varied by signal generator704 or by power source 705. Signal generator 704 also may apply thetiming necessary to synchronize the firing of the fields created bysurface coil 701 with the firing of the fields created by magneticstimulation device 702. Also, the physical and electricalcharacteristics of surface coil 701 may be varied.

In another embodiment, for example, the operating power and timing maybe provided to signal generator 704 by inducing a current fromstimulator circuit 703. In this way, signal generator 704 would receivea signal indicative of the firing and value of the current provided tomagnetic stimulation device 702. This current value may be translated bysignal generator 704 to create the proper strength and timing for themagnetic field(s) created by surface coil 701. The current may beinduced from stimulator circuit 703 using an inductive device (notshown) capable of inducing (and thus measuring) the current provided tomagnetic stimulation device 702 via stimulator circuit 703.

In another embodiment, for example, surface coil 701 may operateindependently of any external signal generator and power source, andsimply generate its magnetic field based on the magnetic field createdby magnetic stimulation device 702. Using this technique focuses on theelectrical and physical characteristics of surface coil 701. In.particular, surface coil 701 may be designed to react to the magneticfield created by magnetic stimulation device 702 in a way that permitstherapeutic magnetic fields to penetrate the patient, while eliminatingor reducing magnetic fields undesirably stimulating surface-proximatenerves, tissue and muscles.

As discussed with reference to FIGS. 1–4, surface coil 701 may be a partof a flexible circuit pad having an adhesive material that permits thepad to be affixed to a treatment location. Alternatively, surface coil701 may be affixed to magnetic stimulation device 702. Also, where morethan one surface coil 701 is used, some surface coils may be attached toa flexible circuit pad, while other surface coils may be affixed tomagnetic stimulation device 702.

FIG. 8 is a block diagram illustrating another technique for reducingdiscomfort caused by electrical stimulation. As shown in FIG. 8, asystem 800 includes a power supply 801 in communication with electrodes802 a and 802 b. Although two electrodes are shown in FIG. 8, it shouldbe appreciated that any number of electrodes may be used.

As previously discussed, magnetic stimulation device 501 createsmagnetic lines of flux 505 a–d, which in turn create electric fields 504a–e. Electric fields 504 a–e induce both desirable and undesirableelectric currents on and within the patient's head 502. System 800overcomes the discomfort created by the undesired electric currents,while permitting the desired electric currents to continue to have theirtherapeutic effect on the patient. In particular, power supply 801provides power (i.e., current and/or voltage) to electrodes 802.Electrodes 802 conduct the power from power supply 801 to the patient'shead 502.

The power provided to electrodes 802 may be substantially constant ortime-varying. When the power is substantially constant, the powerconducted to the patient's head 502 via electrodes 802 creates asubstantially constant electric field in the nerves, muscle and tissuesof the patient that lie in between or proximate to electrodes 802. Theelectric field created by electrodes 802 may have a strength that biasescertain cells (i.e., those that are undesirably stimulated by magneticstimulation device 501). The bias level may be such that the cells arebiased near or above their depolarization level. By biasing the cells ator near their depolarization level, electrolytes for example, areredistributed along the cell, thus reducing the ability of theelectrolytes from being transported across the cell membrane. Reducingthe ability of the electrolytes from being transported across the cellmembrane reduces the possible stimulation of those cells by magneticstimulation device 501, because the cells may not be as capable ofrepeatedly responding to the induced electric field created by magneticstimulation device 501. As a result, the discomfort felt by the patientduring treatment is reduced. Although this example was discussed in thecontext of a substantially constant power source, it should beappreciated that the power need not be applied throughout the entiretreatment, but may for example be turned off at any point after thebeginning of a pulse corresponding to the therapeutic magneticstimulation.

In addition to, or instead of, a substantially constant power supplyprovided when the magnetic stimulation is applied, power provided bypower source 801 may be time-varying. The time-varying signal from powersource 801 may be used to desensitize the muscle, tissue and/or nervesthat undesirably are stimulated by magnetic stimulation device 501. Inparticular, power source 801 may be designed to pre-stimulate (i.e.,prior to the therapeutic pulse applied by magnetic stimulation device501) particular nerves, muscle and/or tissue to reduce their ability toundesirably respond to the otherwise therapeutic pulse.

For example, in the context of TMS, response time constants for corticalnerves typically range from 50 to 100 microseconds, while response timeconstants for peripheral nerves (e.g., scalp) range from 200 to 300microseconds. Because peripheral nerves are slower to recover than thecortical nerves, stimulating the peripheral nerves just prior toapplication of the therapeutic magnetic stimulation reduces theperipheral nerves ability to respond to the therapeutic magneticstimulation, and thus reduces the discomfort the patient feels as aresult of the therapeutic magnetic stimulation.

Although system 800 was discussed in the context of electrodes havingdirect contact with the patient's head 502, it should be appreciatedthat system 800 also may apply electrical energy to the patientinductively, for example, using surface stimulation coils. Furthermore,while system 800 was described in the context of cortical nerves and itsperipheral nerves, it should be appreciated that system 800 may apply toany circumstances where the nerves that are desired to be stimulatedhave an equivalent or faster response time than the nerves that are notdesired to be stimulated. In addition, it should be appreciated that therequired timing and frequency of the biasing or desensitizing signalprovide to the patient may vary with many factors, including thecharacteristics of the patient and the characteristics of magneticstimulation device 501.

System 800 also may be used in combination or independent of a drug thatacts to desensitize the nerves, muscle and tissue that is undesirablystimulated by magnetic stimulation device 501. For example, a topical orinjected drug may be used to desensitize or insulate the nerves, muscleand tissue from the magnetic stimulation. Such procedures may include ananalgesic, anesthetic, muscle relaxant, or paralytic agent, for example.These drugs may be applied prior to the therapeutic treatment frommagnetic stimulation device 501.

FIG. 9 is a flow diagram illustrating a technique 900 for treating apatient using transcutaneous magnetic stimulation. As shown in FIG. 9,in step 901, a magnetic field is directed to a treatment area on thepatient. In step 902, a flexible circuit pad is applied to the treatmentarea, which may include the patient and/or magnetic stimulation device.In step 903, a conductive gel material is applied between the flexiblecircuit pad and the patient. In step 904, the patient is treated withthe magnetic field.

FIG. 10 is a flow diagram illustrating a technique 1000 for treating apatient using transcutaneous magnetic stimulation. As shown in FIG. 10,in step 1001, a portion of the brain is magnetically stimulated. In step1002, a signal is provided to the conductor and in step 1003 an electricand/or magnetic field is created by the conductor. In step 1004, thestrength and location of the electric and/or magnetic field is adjustedas a function of the magnetic stimulation. In step 1005,cutaneous-proximate stimulation is reduced and/or eliminated using theelectric and/or magnetic fields created by the conductor. In step 1006,the patient is treated with the magnetic stimulation. The steps oftechnique 1000 may be accomplished using the systems described withreference to FIGS. 1–8 or any other systems.

As shown in FIGS. 11–18, additional possible conductor configurationsare shown. Again, it should be appreciated that such configurations arenot meant to provide exclusive, but are meant to provide furtherexplanatory details. The invention may include any of the configurationsshown, as well as any combination of those configurations.

As discussed, placement and configuration of the conductors will bedependent on many variables, including the characteristics of thestimulation device, characteristics of the patient, and characteristicsof the conductors, just to name in a few. Although the inventionincludes all such possible configurations, FIG. 19 provides oneparticular example for greater clarity and explanation. In oneembodiment illustrated in FIG. 19, a magnetic core device may beconstructed to be partially hemispherical, extend approximately 220°,and may be constructed of 3% silicone steel laminations. In this oneexample embodiment, the magnetic core device may be wound with eightturns of #8 American Wire Gauge (AWG) wire. The magnetic core devicealso may be composed of M-19 steel that saturates at 1.7 Tesla. Also,the core may be excited at 20,364 AT, RMS, which corresponds to a peakcurrent of 3600 Amperes, delivered at 100% power. Also, the frequency ofthe current may be 5208 Hz, which corresponds to a period of 192microseconds.

The magnetic field created by this device readily penetrates through thebone. In the context of TMS, where the magnetic field desirablystimulates the brain, but undesirably stimulates nerves, muscle andtissue proximate to the scalp, a three dimensional field analysis isillustrated in FIG. 19. As shown in FIG. 19, the electric fieldcirculates around the magnetic field created by a magnetic core device1901. Although the electric field created by magnetic core device 1901is circular, the electric fields created by the conductors typically arenot, except for the local fields produce by the conductors.

FIG. 20 illustrates one possible placement of two conductors 2001 and2002. Conductors 2001 and 2002 are shown located with respect to themagnetic core device 1901, but it should be appreciated that theconductors may be located with reference to any object, including thepatient's head, for example. In this particular example, a voltage ofapproximately 10 volts may be placed on conductor 2001 and a voltage ofapproximately −5 volts may be placed on electrode 2002.

The regions circumscribed by boxes 2003 and 2004 indicate areas wherethe fields created by conductors 2001 and 2002 effectively cancel orreduce the undesirable fields created by magnetic core device 1901.Also, the voltages applied to conductors 2001 and 2002 may be varied toachieve optimal cancellation or reduction of the fields in the desiredregions. There also may be regions in which the fields are not optimallyreduced or eliminated, such as the region circumscribed by box 2005.

In order to determine optimal conductor size, configuration andlocation, the electric field created by magnetic core device 1901,conductor 2001 and conductor 2002 may be considered at numerous specificpoints or locations and be analyzed accordingly. The electric field atany point on the surface from all three sources may be represented bythe following equation:{right arrow over (E)} _(total) ={E _(Z) ^(mag A) +V _(A) E _(Z)^(elec A) −V _(B) E _(Z) ^(elec B) }Φ _(Z) +{E _(Φ) ^(mag A) +V _(A) E_(Φ) ^(elec A) −V _(Φ) E _(Φ) ^(elec B) }Φ _(Φ).  (1)Also, the sum of all the fields may be represented by the followingequation:

$\begin{matrix}{\mathcal{F} = {\sum\limits_{{all}\mspace{14mu}{points}}^{\;}{\sqrt{\begin{matrix}{\left\{ {E_{Z}^{{mag}\mspace{11mu} A} + {V_{A}E_{Z}^{{elec}\mspace{11mu} A}} - {V_{B}E_{Z}^{{elec}\mspace{11mu} B}}} \right\}^{2} +} \\\left\{ {E_{\Phi}^{{mag}\mspace{11mu} A} + {V_{A}E_{\Phi}^{{elec}\mspace{11mu} A}} - {V_{B}E_{\Phi}^{{elec}\mspace{11mu} B}}} \right\}^{2}\end{matrix}}.}}} & (2)\end{matrix}$

E^(mag A) represents the value of the electric field created by magneticcore device 1901 at a particular point. Similarly, E^(elec A) andE^(elec B) represent the values of the electric fields created byconductor 2001 and conductor 2002, respectively, at the same or similarparticular point. Also, E_(Z) is represents the vertical electric fieldand E_(N) represents the azimuthal fields. A computer simulation may beconducted to permit conductor 2001 and conductor 2002 to be varied inlocation, size and configuration to determine optimal field cancellationof the undesirable fields in the desired locations. For example,conductor 2001 and conductor 2002 may be allowed to move vertically,stretch out azimuthally, and have their dimensions adjusted, forexample. Also, the equations may be used to determine the optimalvoltages to apply to conductor 2001 (V_(A)) and to conductor 2002(V_(B)).

FIG. 21 illustrates an embodiment where just one pair of conductors 2101and 2102 are used to reduce the fields created by magnetic core device1901. Typically, one conductor pair may be used to reduce or diminishfields in the area in which the device creates the strongest fieldconcentration (e.g., for magnetic core device 1901 along the axis of thecore). The voltage across conductors 2101 and 2102 may be set at 3.83volts and the conductors each may be approximately ⅛ inch thick. Theexcitation signal may be 20,364 Ampere-turns at 5.2 kilohertz. Conductor2101 and conductor 2102 each are placed approximately 0.8 inches aboveand below the midline of magnetic core device 1901. A one-quartersection is cut from magnetic core device 1901 to aid in visibility.

FIG. 22 graphically depicts the comparison of the electric field createdby magnetic core device 1901 both with and without cancellation by theconductors 2101 and 2102. In particular, as shown in FIG. 22, thepresence of the conductor(s) fold the electric field pattern of magneticcore device 1901 along the core axis at Θ=0, thus shifting it away fromthe axis. As a result, the peak field over the surface drops from 4.91volts/centimeter without cancellation to approximately 4.46volts/centimeter with cancellation.

FIG. 23 illustrates an embodiment where six conductors 2301–2306 areused to reduce the fields created by magnetic core device 1901. In thisparticular example, the six conductors make two voltage pairs, withconductors 2301 and 2302 paired together, while conductors 2303–2306 aregrouped together. As shown in FIG. 23, conductors 2303–2306 each areapproximately 1.5625 inches above and below the midline of magnetic coredevice 1901. Also, conductors 2301 and 2302 each are 0.8125 inches aboveand below the midline of magnetic core device 1901. The width ofconductors 2301 and 2302 each may be 2.52 inches, while the width ofconductors 2303–2306 each may be 1.17 inches. A voltage of 1.86 voltsmay be created between conductors 2301 and 2302, while a voltage of 3.37volts may be created between any pair of conductors 2303–2306. Inaddition, conductors 2301–2306 may be ⅛ inch thick.

With the conductor configuration illustrated in FIG. 23, the peaksurface field of magnetic core device 1901 may be reduced from 4.91volts/centimeter without the cancellation to 4.36 volts/centimeter withcancellation.

As discussed, the voltage waveform to the conductors should be timedwith the generation of fields created by the stimulation device tomaximize desirable cancellation. In particular, the voltage provided tothe conductors may be timed with the current in the stimulation device.FIG. 25 provides just one example embodiment of such a possible timingconfiguration. As shown in FIG. 25, using a magnetic core device andstimulation circuit similar to that discussed with reference to FIGS.19–24, for example, proper timing of the application of voltage signalsto the conductors may be considered with respect to the TMS examplediscussed.

As previously discussed, voltage induced in the skin is proportional tothe derivative of the magnetic field. Also, because conductivity of thestimulation device typically is relatively small, the derivative of themagnetic field created by the stimulation device is substantiallysimilar to the derivative of the current provided to the stimulationdevice. In FIG. 24, the top graph illustrates that the current formagnetic core device 1901 as a function of time is a decaying sinusoid.The lower graph illustrates the accompanying conductor potentialnecessary to realize the field cancellation and/or reduction. Althoughthe current begins at current may begin a zero, the voltage on theelectrode does not. Table I provides an example of the values of theconductor voltage in different configurations along with the corecurrent. Notably, as the magnetic core excitation current scales, somust the conductor voltage also scale.

TABLE I Current and Electrode Voltage versus Time Time Current OneConductor Pair Two Pair A Two Pair B (μs) (A) (V) (V) (V) 5 620 5.2892.568 4.654 10 1100 5.334 2.590 4.693 15 1620 5.416 2.630 4.766 20 21005.406 2.625 4.757 25 2740 4.961 2.409 4.365 30 3100 3.982 1.934 3.504 353580 2.516 1.222 2.214 40 3620 0.858 0.417 0.755 45 3660 −0.590 −0.286−0.519 50 3500 −1.749 −0.849 −1.539 55 3260 −2.589 −1.258 −2.278 60 3020−3.307 −1.606 −2.909 65 2700 −4.011 −1.948 −3.529 70 2220 −4.508 −2.189−3.967 75 1740 −4.666 −2.266 −4.105 80 1300 −4.640 −2.254 −4.083 85 860−4.619 −2.243 −4.064 90 420 −4.677 −2.271 −4.115 95 0 −4.788 −2.325−4.213 100 −560 −4.715 −2.290 −4.148 105 −1040 −4.373 −2.124 −3.848 110−1320 −4.097 −1.990 −3.605 115 −1800 −3.869 −1.879 −3.404 120 −2080−3.515 −1.707 −3.093 125 −2520 −2.873 −1.395 −2.528 130 −2720 −1.908−0.927 −1.679 135 −2840 −0.883 −0.429 −0.777 145 −2840 1.082 0.526 0.952150 −2640 1.879 0.912 1.653 155 −2440 2.470 1.200 2.174 160 −2240 2.9911.452 2.632 165 −1800 3.290 1.598 2.894 170 −1560 3.418 1.660 3.008 175−1200 3.561 1.729 3.133 180 −920 3.655 1.775 3.216 185 −480 3.439 1.6703.026 190 −160 2.690 1.306 2.367 195 100 1.532 0.744 1.348 200 220 0.3100.150 0.273 205 0 −0.358 −0.174 −0.315 210 0 −0.463 −0.225 −0.408

It is to be understood that the foregoing illustrative embodiments havebeen provided merely for the purpose of explanation and are in no way tobe construed as limiting of the invention. Words used herein are wordsof description and illustration, rather than words of limitation. Inaddition, the advantages and objectives described herein may not berealized by each and every embodiment practicing the present invention.Further, although the invention has been described herein with referenceto particular structure, materials and/or embodiments, the invention isnot intended to be limited to the particulars disclosed herein. Rather,the invention extends to all functionally equivalent structures, methodsand uses, such as are within the scope of the appended claims. Thoseskilled in the art, having the benefit of the teachings of thisspecification, may affect numerous modifications thereto and changes maybe made without departing from the scope and spirit of the invention.

1. A method for reducing discomfort caused by transcutaneousstimulation, comprising: providing transcutaneous stimulation to a firstlocation; locating at least one conductive material at a secondlocation; and reducing discomfort caused by the transcutaneousstimulation at the second location using the conductive material.
 2. Themethod of claim 1, further comprising shielding a magnetic field createdby the transcutaneous stimulation using the conductive material.
 3. Themethod of claim 1, wherein the conductive material is at least oneconductor.
 4. The method of claim 1, further comprising shielding anelectric field created by the transcutaneous stimulation using theconductive material.
 5. The method of claim 1, further comprisingadjusting characteristics of the conductive material as a function ofthe transcutaneous stimulation.
 6. The method of claim 5, wherein thecharacteristics include at least one of the following: conductivity,inductance, length, width, aspect ratio and surface area.
 7. The methodof claim 1, further comprising treating the first location with thetranscutaneous stimulation.
 8. The method of claim 1, further comprisingredistributing a magnetic field created by the transcutaneousstimulation using the conductive material.
 9. The method of claim 1,further comprising redistributing an electric field created by thetranscutaneous stimulation using the conductive material.
 10. The methodof claim 1, further comprising disrupting a flow of electrical currentto the second location.
 11. The method of claim 10, wherein the flow ofelectrical current is created by the transcutaneous stimulation.
 12. Themethod of claim 1, further comprising applying the transcutaneousstimulation to a patient's head.
 13. The method of claim 12, furthercomprising applying the conductive material in proximity to a trigeminalnerve.
 14. The method of claim 12, further comprising customizing theconductive material to locally protect the second location.
 15. Themethod of claim 1, further comprising modifying a shape of theconductive material as a function of the characteristics of fieldscreated by the transcutaneous stimulation.
 16. The method of claim 1,further comprising modifying the conductive material to provide a largerconductive path for the transcutaneous stimulation at the secondlocation.
 17. The method of claim 1, further comprising configuring theconductive material to be in a substantially perpendicular arrangementwith respect to an electric field created by the transcutaneousstimulation.
 18. The method of claim 1, further comprising directing anelectrical current carried by the conductive material to the secondlocation.
 19. The method of claim 18, wherein the electrical currentreduces discomfort created by the transcutaneous stimulation byelectrically biasing the second location.
 20. The method of claim 18,wherein the electrical current is induced on the conductive material bythe transcutaneous stimulation.
 21. The method of claim 1, furthercomprising attaching the conductive material to the second location. 22.The method of claim 1, further comprising attaching the conductivematerial to a device that provides the transcutaneous stimulation. 23.The method of claim 1, further comprising reducing a field generated bythe conductive material.
 24. The method of claim 1, further comprisingsubstantially blocking a field generated by the conductive material fromreaching a device that provides the transcutaneous stimulation.
 25. Themethod of claim 24, further comprising substantially passing a fieldgenerated by the transcutaneous stimulation device to the conductivematerial.
 26. The method of claim 1, further comprising adjusting atleast one characteristic of the conductive material as a function of atleast one of the following: shape of the first location, size of thefirst location, shape of the second location, size of the secondlocation, density of hair at the first location.
 27. The method of claim1, further comprising determining at least one characteristic of thetranscutaneous stimulation using the conductive material.
 28. The methodof claim 27, further comprising adjusting the transcutaneous stimulationas a function of the determining.
 29. The method of claim 28, furthercomprising treating the first location with the transcutaneousstimulation and conducting the adjusting of the transcutaneousstimulation prior to the treating of the first location.
 30. The methodof claim 27, wherein the characteristics include at least one of thefollowing: a strength of a magnetic field, a location of a magneticfield, a strength of an electric field, a location of an electric field.31. The method of claim 1, wherein the transcutaneous stimulation ismagnetic stimulation and further comprising determining a characteristicof a magnetic field created by the transcutaneous magnetic stimulationusing the conductor.
 32. The method of claim 31, further comprisingproviding an indication of the determined characteristic.
 33. The methodof claim 31, further comprising providing an indication of when thedetermined characteristic satisfies a predetermined threshold.
 34. Themethod of claim 31, wherein the characteristic comprises at least one ofthe following: a strength of the magnetic field and a location of themagnetic field.
 35. A system for reducing discomfort caused bytranscutaneous stimulation, comprising: a transcutaneous stimulationdevice that creates a magnetic field for treating a first location; andat least one conductive material at a second location and locatedsubstantially within the magnetic field, wherein the conductive materialreduces discomfort caused by the transcutaneous stimulation at thesecond location.
 36. The system of claim 35, wherein the conductivematerial shields a magnetic field created by the transcutaneousstimulation device.
 37. The system of claim 35, wherein the conductivematerial is at least one conductor.
 38. The system of claim 35, whereinthe conductive material shields an electric field created by thetranscutaneous stimulation device.
 39. The system of claim 35, whereinat least one characteristic of the conductive material is determined asa function of the transcutaneous stimulation device.
 40. The system ofclaim 39, wherein the characteristics include at least one of thefollowing: conductivity, inductance, length, width, aspect ratio andsurface area.
 41. The system of claim 35, wherein the conductivematerial redistributes a magnetic field created by the transcutaneousstimulation device.
 42. The system of claim 35, wherein the conductivematerial redistributes an electric field created by the transcutaneousstimulation device.
 43. The system of claim 35, wherein the conductivematerial disrupts a flow of electrical current to the second location.44. The system of claim 43, wherein the flow of electrical current iscreated by the transcutaneous stimulation.
 45. The system of claim 35,wherein the transcutaneous stimulation is applied to a patient's head.46. The system of claim 35, wherein the conductive material is locatedin proximity to a trigeminal nerve.
 47. The system of claim 35, whereinthe conductive material is located to protect the second location fromthe transcutaneous stimulation device.
 48. The system of claim 35,wherein the conductive material is configured as a function of thecharacteristics of fields created by the transcutaneous stimulation. 49.The system of claim 35, wherein the conductive material is configured toprovide a larger conductive path for the transcutaneous stimulation atthe second location.
 50. The system of claim 35, wherein the conductivematerial provides a path of relatively lesser resistance for thetranscutaneous stimulation at the second location.
 51. The system ofclaim 35, wherein the conductive material is configured to be in asubstantially perpendicular arrangement with respect to an electricfield created by the transcutaneous stimulation.
 52. The system of claim35, wherein the conductive material carries an electrical current to thesecond location.
 53. The system of claim 52, wherein the electricalcurrent reduces discomfort created by the transcutaneous stimulationdevice by electrically biasing the second location.
 54. The system ofclaim 52, wherein the electrical current is induced on the conductivematerial by the transcutaneous stimulation device.
 55. The system ofclaim 35, wherein the conductive material is attached to the secondlocation.
 56. The system of claim 35, wherein the conductive materialattaches to the transcutaneous stimulation device.
 57. The system ofclaim 35, further comprising a blocking component that reduces a fieldgenerated by the conductive material.
 58. The system of claim 57,wherein the blocking component blocks a field generated by theconductive material from reaching the transcutaneous stimulation device.59. The system of claim 57, wherein the blocking component substantiallypasses a field generated by the transcutaneous stimulation device to theconductive material.
 60. The system of claim 35, wherein acharacteristic of the conductive material is a function of at least oneof the following: shape of the first location, size of the firstlocation, shape of the second location, size of the second location,density of hair at first location.
 61. The system of claim 35, whereinthe conductive material is used to determine at least one characteristicof the transcutaneous stimulation device.
 62. The system of claim 61,wherein an output of the transcutaneous stimulation device is adjustedas a function of the characteristic prior to the treating of the firstlocation.
 63. The system of claim 61, wherein the characteristicsinclude at least one of the following: a strength of a magnetic field, alocation of the magnetic field, a strength of an electric field, alocation of the electric field.
 64. The system of claim 35, wherein thetranscutaneous stimulation is magnetic stimulation and furthercomprising a feedback circuit in communication with the conductor andthe transcutaneous magnetic stimulation device, wherein the feedbackcircuit provides a characteristic of a magnetic field created by thetranscutaneous magnetic stimulation from the conductor.
 65. The systemof claim 64, further comprising an indicator device in communicationwith the feedback circuit, wherein the indicator reflects a value of thecharacteristic.
 66. The system of claim 65, wherein the indicator deviceprovides an indication of when the characteristic satisfies apredetermined threshold.
 67. The system of claim 64, wherein thecharacteristic comprises at least one of the following: a strength ofthe magnetic field and a location of the magnetic field.
 68. The systemof claim 35, wherein the conductive material is at least one coil havinga predetermined number of turns.
 69. The system of claim 35, wherein theconductive material comprises a ferrite material.
 70. The system ofclaim 35, wherein the conductive material reduces eddy currents inducedby the transcutaneous stimulation device.
 71. The system of claim 35,wherein the conductive material is comprised of a material that reducesheating.
 72. The system of claim 35, wherein each conductive materialhas different characteristics as a function of their location.